A liquid crystal display device capable of color display comprises a display panel. The display panel comprises pixels which are arranged in rows and columns (along an X-axis and a Y-axis). The X-axis orthogonally intersects the Y-axis. Each of the pixels comprises a color filter and operates as a red (R) sub-pixel, a green (G) sub-pixel, or a blue (B) sub-pixel.
In recent years, a technique of improving display luminance of a display panel has been proposed. As an example, an R sub-pixel, a G sub-pixel, a B sub-pixel, and a white (W) sub-pixel are arranged in a row in a predetermined order, and these four sub-pixels form one set that constitutes one pixel. The white (W) sub-pixel is higher in light utilizing efficiency than any of the R sub-pixel, the G sub-pixel, and the B sub-pixel, and is three times as high in transmittance as any of the R sub-pixel, the G sub-pixel, and the B sub-pixel. Therefore, use of a white sub-pixel (W) in a composite color unit pixel will raise a display device in display intensity.
However, external devices that are used to supply video data (which may also be called image data) to a display panel generally output RGB video signals. Namely, conventional external devices do not output W video signals for W sub-pixels. This is because a video signal generally comprises an R video signal component, a G video signal component, and a B video signal component.
If the above-mentioned new type display panel and a conventional external device are integrated with each other to form a liquid crystal display device, the following new problems will occur.
(1) A new conversion circuit will be required to generate W video signals.
(2) Provision of a conversion circuit will increase the number of sub-pixels from three (an R sub-pixel, a G sub-pixel, and a B sub-pixel) to four (an R sub-pixel, a G sub-pixel, a B sub-pixel, and a W sub-pixel). Therefore, a total count of data pieces required for driving a liquid crystal display device will increase. As a result, time required for transmission of data will be long and electric power consumption will increase.
(3) Data processing will be complicated.